'mozrestart' does restart your firefox/thunderbird if they are running MozRepl.

Options:
-help this message
-host Firefox/Thunderbird's MozRepl host (default localhost)
If $ENV{MOZREPL_HOST} was existed, then the env value will be using instead of this value.
-port Firefox/Thunderbird's MozRepl port (default 4242)
If $ENV{MOZREPL_PORT} was existed, then the env value will be using instead of this value.
Examples:
mozrestart
mozrestart -port=1234
env MOZREPL_PORT=1234 mozrestart